1. Field of the Invention
The present invention relates to a resist composition and a method of forming a resist pattern, as well as to a polymeric compound that is useful for use within the resist composition, and a method of producing the same.
Priority is claimed on Japanese Patent Application No. 2011-123261, filed Jun. 1, 2011, the content of which is incorporated herein by reference.
2. Description of Related Art
In lithography techniques, for example, a resist film composed of a resist material is formed on a substrate, and the resist film is subjected to selective exposure followed by development, thereby forming a resist pattern having a predetermined shape on the resist film. A resist material in which the exposed portions of the resist film become soluble in a developing solution is called a positive-type, and a resist material in which the exposed portions become insoluble in a developing solution is called a negative-type.
In recent years, in the production of semiconductor elements and liquid crystal display elements, advances in lithography techniques have led to rapid progress in the field of pattern miniaturization.
Typically, these pattern miniaturization techniques involve shortening the wavelength (and increasing the energy) of the exposure light source. Conventionally, ultraviolet radiation typified by g-line and i-line radiation has been used, but nowadays KrF excimer lasers and ArF excimer lasers are starting to be introduced in the mass production of semiconductor elements. Furthermore, research is also being conducted into lithography techniques that use an exposure light source having a shorter wavelength (and a higher energy level) than these excimer lasers, such as extreme ultraviolet radiation (EUV), electron beam (EB), and X-ray.
Resist materials for use with these types of exposure light sources require lithography properties such as a high resolution capable of reproducing patterns of minute dimensions, and a high level of sensitivity to these types of exposure light sources.
As a resist material that satisfies these conditions, conventionally a chemically amplified composition has been used, which includes an acid generator component that generates acid upon exposure, and a base component that exhibits changed solubility in a developing solution under the action of acid.
Resins (base resins) are typically used as the base components used within chemically amplified resist compositions.
For example, in an alkali developing process where an alkali developing solution is used as a developing solution, a chemically amplified resist composition for forming a positive resist pattern typically contains an acid generator component and a resin component that exhibits increased solubility in an alkali developing solution under the action of acid. If the resist film formed using this resist composition is selectively exposed during formation of a resist pattern, then acid is generated from the acid generator component within the exposed portions, and the action of this acid causes an increase in the solubility of the resin component in an alkali developing solution, making the exposed portions soluble in the alkali developing solution. As a result, by performing alkali developing, the unexposed portions remain as a pattern, resulting in the formation of a positive-type pattern.
As the resin component, a resin that exhibits increased polarity under the action of acid is typically used. When the polarity of the resin is increased, the solubility in an alkali developing solution increases whereas the solubility in an organic solvent decreases. Accordingly, if a solvent developing process that uses a developing solution containing an organic solvent (an organic developing solution) is employed instead of the alkali developing process, then within the exposed portions of the resist film, the solubility in the organic developing solution decreases relatively, meaning that during the solvent developing process, the unexposed portions of the resist film are dissolved in the organic developing solution and removed, whereas the exposed portions remain as a pattern, resulting in the formation of a negative-type resist pattern. This type of solvent developing process that results in the formation of a negative-type resist pattern is sometimes referred to as a negative-type developing process (for example, see Patent Document 1).
Currently, resins that contain structural units derived from (meth)acrylate esters within the main chain (acrylic resins) are widely used as base resins for chemically amplified resist compositions that use ArF excimer laser lithography or the like, as they exhibit excellent transparency in the vicinity of 193 nm (for example, see Patent Document 2).
In order to improve various lithography properties, a plurality of structural units are introduced in the base resin. For example, in the case of a resin component that exhibits higher polarity under the action of acid, a base resin is typically used that includes not only a structural unit having an acid-degradable group that exhibits higher polarity by degrading under the action of the acid generated from the acid generator, but also a structural unit having a polar group such as a hydroxyl group, and a structural unit having a lactone structure.
In particular, the structural units having a polar group are widely used, since the compatibility with an alkali developing solution is improved, which contributes to favorable improvements in the resolution. A structural unit having a lactone structure is generally considered as being effective in improving the adhesion between the resist film and the substrate, and increasing the compatibility with an alkali developing solution, thereby contributing to improvement in various lithography properties.
Here, the term “(meth)acrylate ester” is a generic term that includes either or both of the acrylate ester having a hydrogen atom bonded to the α-position and the methacrylate ester having a methyl group bonded to the α-position. The term “(meth)acrylate” is a generic term that includes either or both of the acrylate having a hydrogen atom bonded to the α-position and the methacrylate having a methyl group bonded to the α-position. The term “(meth)acrylic acid” is a generic term that includes either or both of acrylic acid having a hydrogen atom bonded to the α-position and methacrylic acid having a methyl group bonded to the α-position.
In recent years, with increasing demands for high resolution resist patterns of 0.15 microns or smaller, in addition to the above-mentioned improvement of various lithography properties and the like, improving the level of defects following developing (namely, surface defects) is now also becoming more necessary. Here, the term “defects” refers to general abnormalities of a resist pattern, which are detected when observed from right above the developed resist pattern, using a surface defect detection apparatus (product name: “KLA”) manufactured by KLA-TENCOR Corporation. Examples of these “abnormalities” include post-developing blobs, scum, foam, dust and bridges between resist patterns.
As a method of improving such defects, for example, in the base resin, it is possible to lower the proportion of the structural unit having a highly hydrophobic, acid decomposable group, or to increase the proportion of the structural unit having a polar group. As a method of improving defects using the latter approach, a base resin having a structural unit that includes an oxo group (═O) has been disclosed in Patent Document 3. Further, as a monomer for deriving the structural unit having an oxo group or a monomer, obtained from the above monomer, for deriving the structural unit having a lactone structure, those described in Patent Document 4 are known.